Exemplary embodiments of the invention generally relate to torque limiters, and more particularly, to torque limiters for applications having lower torque limits and tight tolerances.
Propulsion systems of a vehicle, such as a rotary wing aircraft for example, include a permanent magnet alternator (PMA) driven by an engine or turbine through a driving gearbox. The normal drive torque and the maximum torque capability of the driving gearbox are substantially similar and the gearbox must provide the normal drive torque under all operating conditions with little or no potential for failure. Conventional PMAs typically do not include a torque limiting feature to prevent a catastrophic failure in the event that the PMA rotor jams.
When the PMA is replaced in the field, there is an increased possibility of debris or other foreign material entering into the system and affecting the functionality of the system. Consequently, there is a need for a torque limiting device. However, where the system is a propulsion system of rotary wing aircraft, size constraints, large operating temperature range, and relatively small torque limits prevent the use of conventional torque limiting devices, such as keyways and shaft section shearing for example. As a result, a conventional torque limiting device is difficult to implement in such restrictive applications having low torque limits with tight tolerances.